The invention relates generally to damping of machine spindles and the like and, specifically, the invention relates to machines and other equipment having a relatively long working bar extending from the main machine body, where the bar is subjected to vibrational movements.
Machines such as horizontal boring machines and other similar machine tools are typically constructed so that a machine spindle or boring bar may slide relative to the machine base so that the tool tip at the outermost bar end is moved from a working position proximal to the machine base, to a fully-extended position distal to the machine base.
The extensible boring bar is effectively supported in two different manners at its extreme adjusting positions. When proximal the machine spindle base, the spindle behaves in a relatively simply supported manner, and is loaded at or near the first support, i.e. the snout of the machine. When fully-extended, the machine bar is basically cantilevered beyond the same two support points, and an intermediate deflection seen at the spindle is between the two support points. In the fully-retracted or simply supported, position, the maximum deflection seen by the spindle is at the snout, or end support. While no prior art patents attempt to solve the problem of vibrations occurring on such an extensible bar, several patents are generally noteworthy in the hydraulic damper art, as follows:
U.S. Pat. No. 3,747,470 --Inoue et al: attempts to place a vibration damper at or near the loading point of a spindle, i.e. between the spindle bearing and the loading point of a spindle, whereas prior art devices attempt to place the support bearing up close to the loading point for high static stiffness. The device further teaches a viscous fluid film device with controlled fluid flow through the device. Inoue does not teach a mechanism whereby an extensible bar is moved between a relatively simply supported state to a two-support cantilever-load supported condition.
U.S. Pat. No. 3,836,215--Dopkins: teaches a single damper ring, wherein the damper ring contains a shaft bearing but the particular bearing does not support any load. The damper ring device features a bleed conduit so that viscous fluid may flow through the device. The bearing/damper ring is placed between a pair of load supporting bearings which effectively carry a shaft in a simply-supported manner. It is assumed, but not shown, in Dopkins tha the load is an overhung load and that the maximum deflection of the shaft would be between the load supporting bearings.
U.S. Pat. No. 3,897,985--Davis et al: teaches a squeeze films shaft damper, having an annular ring around a shaft end bearing which is filled with fluid and sealed with O-rings. The Davis patent does not teach how or where the load is applied to the shaft.
U.S. Pat. No. 3,980,358--Davis: a vertical assembly (FIGS. 1, 2 and 3) is depicted with an annular squeeze film damper around the bottom shaft and bearing. The device also features an axial damper flange on the radial end bearing damper.
U.S. Pat. No. 4,084,861--Greenberg: teaches a cantilevered bearing support with an annular damping ring around the spindle end bearing, which is designed to bottom out against a damper support which, in turn is likewise cantilever-mounted with a predetermined spring rate. The Greenberg patent does not teach the use of any other bearings to support the shaft, nor does it relate the device to a specific shaft loading point.
U.S. Pat. No. 3,456,992--Kulina: teaches a radial damper ring around a shaft bearing, wherein the ring is cantilever-mounted to a base, and the device has a controlled orifice leakage for a viscous damping fluid.
With regard to the types of machines to which the instant invention may be applied, U.S. Pat. No. 3,540,346--Jones, discloses a typical, undamped, horizontal boring machine with a hydraulically-actuated clamping sleeve for the boring bar.
Applicant has addressed the problem of damping the extensible boring bar and has solved it in a unique manner with a compound squeeze film damping device.
It is therefore an object of the present invention to effectively damp vibrations in a boring bar and other like bar-type machines wherein the boring bar is extensible between positions proximal to a machine base and distal to the machine base.